..Compression Test..??? Explanation..
Thread Starter
Burning Brakes
Joined: Jul 2006
Posts: 875
Likes: 1
..Compression Test..??? Explanation..
Could someone give my a quick rundown on what a compression
test checks for ?...and would you recommend this to be done on
a car before you buy it ?...or only on a car that you had alot
of questions about ?
test checks for ?...and would you recommend this to be done on
a car before you buy it ?...or only on a car that you had alot
of questions about ?
Safety Car
Joined: Jul 2005
Posts: 4,743
Likes: 0
From: Omaha Nebraska
St. Jude Donor '06
Ummm it checks for compression...
And you might want to get one if you had lots of questions or mabye only a few questions... The number of questions has nothing to do with it. However, depending on what the questions were in regards to, then that's different!! 
OK, sorry.. I had too...
Is the car high mileage? Does it run poorly? Does it have a miss?
Compression checks are done when you suspect excessive ring wear, or maybe you feel the valves are leaking and not closing properly because they might be burnt or several other things... It depends... If you do a compression check and you have a couple cylinders side by side that are bad, you could have a head gasket issue too.
It's a diagnostic tool used to further investigate an engine that has problems. However you check it before you do a teardown, so it can give you an IDEA of what MAY be wrong... for sure it will tell you this cylinder or that cylinder has issues, and or problems. Then you start there and see what needs to be fixed.
Tell us more about why you think you need one... 
And you might want to get one if you had lots of questions or mabye only a few questions... The number of questions has nothing to do with it. However, depending on what the questions were in regards to, then that's different!! OK, sorry.. I had too...
Is the car high mileage? Does it run poorly? Does it have a miss?
Compression checks are done when you suspect excessive ring wear, or maybe you feel the valves are leaking and not closing properly because they might be burnt or several other things... It depends... If you do a compression check and you have a couple cylinders side by side that are bad, you could have a head gasket issue too.
It's a diagnostic tool used to further investigate an engine that has problems. However you check it before you do a teardown, so it can give you an IDEA of what MAY be wrong... for sure it will tell you this cylinder or that cylinder has issues, and or problems. Then you start there and see what needs to be fixed.
Tell us more about why you think you need one...
Pro
Joined: May 2005
Posts: 592
Likes: 17
From: Tempe AZ
A compression checks will help show you how much the engine has been used by how close the compression figures are to new specs. Plus if ONE cylinder is really different than the others you many have problems.
Next in line is a leak down test to see if the engine maintains the compression.
Both of these tests are pretty standard if you ask a shop to check out a car for you pre-purchase.
Next in line is a leak down test to see if the engine maintains the compression.
Both of these tests are pretty standard if you ask a shop to check out a car for you pre-purchase.
